linux-kernel - Re: [uml-devel] [PATCH 01/14] uml: fix compilation options for USER

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Message-ID: <20061011110828.43576.qmail@web25221.mail.ukl.yahoo.com>
Date:	Wed, 11 Oct 2006 13:08:27 +0200 (CEST)
From:	Paolo Giarrusso <blaisorblade@...oo.it>
To:	Jeff Dike <jdike@...toit.com>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [uml-devel] [PATCH 01/14] uml: fix compilation options for USER_OBJS

Jeff Dike <jdike@...toit.com> ha scritto: 

> On Thu, Oct 05, 2006 at 11:38:36PM +0200, Paolo 'Blaisorblade'
> Giarrusso wrote:
> > Again, move inclusion of arch's Makefile after CFLAGS setting - I
> remember
> > merging the same patch eons ago in 2.6, so I added a comment.
> > 
> > I discovered this because debug info weren't enabled for
> USER_OBJS - they're
> > compiled with USER_CFLAGS which is calculated from CFLAGS (the
> whole thing is a
> > bit of an hack but fixing it is not easy, so we're leaving it
> as-is).
> 
> What's the matter with this:
> 
> Index: linux-2.6.18-mm/arch/um/Makefile
> ===================================================================
> --- linux-2.6.18-mm.orig/arch/um/Makefile       2006-10-03
> 17:44:32.000000000 -0400
> +++ linux-2.6.18-mm/arch/um/Makefile    2006-10-09
> 12:29:32.000000000 -0400
> @@ -64,9 +64,8 @@ CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSU
>  
>  AFLAGS += $(ARCH_INCLUDE)
>  
> -USER_CFLAGS := $(patsubst -I%,,$(CFLAGS))
> -USER_CFLAGS := $(patsubst -D__KERNEL__,,$(USER_CFLAGS))
> $(ARCH_INCLUDE) \
> -       $(MODE_INCLUDE) -D_FILE_OFFSET_BITS=64
> +USER_CFLAGS = $(patsubst -D__KERNEL__,,$(patsubst -I%,,$(CFLAGS)))
> \
> +       $(ARCH_INCLUDE) $(MODE_INCLUDE) -D_FILE_OFFSET_BITS=64
>  
>  # -Derrno=kernel_errno - This turns all kernel references to errno
> into
>  # kernel_errno to separate them from the libc errno.  This allows
> -fno-common
> 
> The real problem is the use of := which assigns USER_CFLAGS from
> the
> current value of CFLAGS, which is incomplete, as you noted.

Ok, at a first glance this alternative solution is ok. Make sure (run
gdb on an userspace object file and saying list <function>) that it
works and we'll be ok.

> Moving the include around seems slightly bogus, since its precise
> location shouldn't matter.
> 
> If we switch to plain =, then it will be lazy-evaluated with the
> full
> CFLAGS.
> 
> And we should check other uses of := to make sure they don't have
> similar problems.

Maybe, but I hope not... however if CFLAGS is used elsewhere its
occurrences must be looked for and checked.
--
Paolo 'Blaisorblade' Giarrusso

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